This cell-surface-associated serine exopeptidase is found in the Gram-negative, anaerobic bacterium Porphyromonas gingivalis, which has been implicated in adult periodontal disease [1]. The enzyme releases the N-terminal tripeptide of peptides, such as interleukin-6. It has an absolute requirement for a proline residue at the P1 position but is completely inactivated by a proline residue at the P1′ position [1]. The size of the peptide does not affect the rate of reaction [1].